The photovoltaic effect was first described in 1839 by French physicist A. E. Becquerel. However, it was not until after World War II that Russell S. Ohl invented and patented the modern junction semiconductor solar cell (in 1946). See U.S. Pat. No. 2,402,662. It was not until the mid-1970's that practical and effective gallium-arsenide (GaAs) solar cells became commercially available.
In the decades since, the science and technology related to solar energy conversion has grown considerably. Current commercially available solar arrays (i.e., photovoltaic arrays) are approaching their theoretical maximum efficiency for converting sunlight directly into electricity.
Many involved in solar energy development, deployment, and refinement believe that the use of electrical devices (motors, fans, and the like) should be minimized in the design of solar arrays because of component energy use and maintenance requirements. Although that was an appropriate strategy in the past, it no longer applies in many situations. Highly efficient, low energy and low maintenance devices have concurrently evolved dramatically since the 1970's. Evolution of integrated circuit (IC)-controlled electrical components, heat-sensing and heat-use devices, alignment tools and optics, etc. have coalesced with advancing science and technology from many fields. When the use of electrical energy to power a sub-device is the proximate cause of an increase in overall renewable-energy output, it should be considered as an optional component for renewable energy purposes.
Because solar panels themselves are converging on their theoretical maximum efficiencies, ancillary devices and processes need to be considered to improve the net electrical output of solar arrays. Further still, maintenance requirements, environmental risks, raw materials scarcity, zoning restrictions on large solar arrays, and many other factors must be considered in parallel with efforts to increase energy output from solar arrays. In short, the ultimate goal is not simply increased watts of electricity per photovoltaic installation. A great many other factors unrelated to energy output must also be included in the calculus.
A large number of U.S. patents address various aspect of improving the electrical output of solar arrays. For example:
U.S. Pat. No. 6,274,860 to Rosenberg describes a holographic planar concentrator (HPC) for collecting and concentrating optical radiation. The device is mounted in the intended orientation for collecting solar energy and at least one solar energy-collecting device is mounted along at least one edge of the holographic planar concentrator.
U.S. Pat. No. 6,087,579 to Muskatevc describes a photovoltaic array including a plurality of planar cells, arranged in panels, a light collecting body having a solar energy collecting surface adapted to be oriented for receiving solar energy in a nominal direction which defines a nominal light source direction. The panels are spaced apart from each other in a direction perpendicular to the nominal light source direction and each has an active surface oriented on the body at an angle of less than 90° relative to the nominal light source direction. The light collecting body redirects light received on the light collecting surface onto the active surfaces of the panels.
U.S. Pat. No. 5,409,550 to Safir describes a solar cell module having a housing with at least one aperture associated with a concentrator. Light energy propagated along the optical principal axis of the concentrator passes through the aperture and is concentrated on a primary photoactive area. A secondary photoactive area is also disposed in the housing so as to be illuminated by light energy which is propagated in a direction different from the optical principal axis of the concentrator.
U.S. Pat. No. 6,964,486 to Rabinowitz describes an apparatus for aligning solar concentrator micro-mirrors to maximize the percentage of incident light that is reflected to a photo-active surface.
U.S. Pat. No. 6,294,723 to Uematsu et al. describes a photovoltaic module including a plurality of concentrators each having a light-incident plane and a reflection plane, and photodetectors. Each photodetector is in contact with one of the concentrators. The module is capable of trapping light and generating power even when it is not aligned with the sun.
U.S. Pat. No. 7,000,608 to Löschmann describes a solar plant with at least two solar units. Each of the solar units includes a securing device and a swivel-located supporting structure mounted on it. The solar modules or collectors are mounted on the supporting structure, which can follow the course of the sun by way of its rotational axis.
U.S. Pat. No. 7,394,016 to Gronet describes a solar cell assembly comprising a plurality of elongated solar cells. Each elongated solar cell has an elongated conductive core configured as a first electrode, a semiconductor junction circumferentially disposed on the elongated conductive core, and a transparent conductive oxide layer disposed on the semiconductor junction. Each solar cell is bound to two corresponding metal counter-electrodes that lie in a groove running lengthwise along the solar cell. The solar cell also includes a plurality of internal reflectors. Each reflector is disposed between two of the elongated solar cells such that a portion of the solar light reflected from internal reflector is reflected onto the two elongated cells.
U.S. Pat. No. 5,990,413 to Ortabasi describes a laminated, bifacial solar cell that can receive and convert sunlight incident on either side of the solar cell. The laminate is held in a frame by high tensile cords that are strung like the cords in a tennis racket. The resulting assembly receives direct sunlight from one side and reflected light on the other side.
U.S. Pat. No. 4,169,738 to Luque describes another planar solar cell that is active on both sides. The solar cell is positioned in a solar concentrator capable of simultaneously illuminating both sides of the cell. The cell is immersed in a transparent liquid that enhances solar energy concentration and aids in removing undesirable heat from the cell. Electrically conductive metal grids serving as cathode and anode connections are formed on both sides of the cell. The grid apertures allow the light to enter into the appropriate semiconductor regions.